Fracturing a well formation

ABSTRACT

A fracturing tool includes a container structure, and a puncher charge arranged in the container structure, where the puncher charge if detonated is configured to extend an opening through the container structure without creating a perforation tunnel in a formation surrounding the well. An energetic material is to be initiated by detonation of the puncher charge, where the energetic material upon initiation creates an increased pressure in the well to perform fracturing of the formation.

CROSS-REFERENCE TO RELATED APPLICATION

This claims priority under 35 U.S.C §119(e) of Chinese Patent Application No. 201210327368.X, filed Sep. 6, 2012, which is hereby incorporated by reference.

BACKGROUND

Fracturing can be performed in a subterranean formation to propagate fractures in the formation. The fractures provide passageways in the formation through which fluids can flow to or from a well (for production or injection operations, respectively). Fracturing the formation improves the fluid transmissivity of the formation, such that more efficient fluid production can be accomplished.

SUMMARY

In general, according to some implementations, a fracturing apparatus for use in a well includes a container structure, a puncture charge arranged in the container structure, where the puncher charge if detonated is configured to extend an opening through the container structure without creating a perforation tunnel in a formation surrounding the well. Additionally, the fracturing apparatus includes an energetic material to be initiated by detonation of the puncher charge, where the energetic material upon initiation creates increased pressure in the well to perform fracturing of the formation.

Other or alternative features will become apparent from the following description, from the claims, and from the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments are described with respect to the following figures:

FIGS. 1 and 3 are partial sectional views of fracturing tools according to some implementations;

FIG. 2 is a cross-sectional view of a portion of the fracturing tool of FIG. 1, in accordance with some implementations;

FIG. 4 illustrates an example tool string having a fracturing tool configured according to some implementations; and

FIG. 5 is a flow diagram of a process of forming a fracturing tool according to some implementations.

DETAILED DESCRIPTION

To fracture a formation surrounding a well, a fracturing tool can be deployed into the well. The fracturing tool can have an energetic material that upon initiation produces increased pressure in the well, where the increased pressure is provided to perform fracturing in the formation. Generally, fracturing the formation helps to improve fluid communication characteristics of the formation. Fracturing also helps to relieve plugging of communications channels in the formation due to debris. Additionally, formation breakdown pressure can be reduced.

Traditional fracturing tools are designed for relatively shallow wells, such as wells with depths less than 5,000 meters (m). At depths greater than 5,000 m (and sometimes even greater than 7,500 m or 10,000 m), relatively high downhole temperatures and pressures can raise various issues relating to reliability of a fracturing tool. To withstand elevated downhole pressures in a deep well, for example, a container structure can be provided to carry components that may be sensitive to the elevated downhole pressures. However, if improperly designed, the container structure may not be properly broken apart during operation, which can prevent initiation of an energetic material of the fracturing tool.

In other designs, an initiating material can be provided on the outside of the housing of a tool, such as in the form of a sleeve formed of the initiating material that can be fitted around the tool housing. However, such designs may suffer from inadvertent self-ignition of the initiating material due to friction between the initiating material and an inner wall of the well during deployment of the tool.

In accordance with some implementations, fracturing tools are provided that are able to operate in relatively deep wells, such as wells having depths of greater than 5,000 m, 7,500 m, or 10,000 m. In other examples, fracturing tools according to some implementations can also be used in relatively shallow wells. In some implementations, a fracturing tool can use an energetic material that is able to withstand the relatively high temperatures and high pressures of a relatively deep well. In other implementations, a sealed housing can be provided to protect the energetic material from elevated downhole temperature and pressure conditions, such that the energetic material having reduced temperature and pressure ratings may be used. In addition, a relatively reliable ignition mechanism can be provided in the fracturing tool to ignite the energetic material.

In some implementations, the energetic material can include any one or combination of the following: a propellant, a high explosive, a gun powder, a combustible metallic powder, and thermite. The energetic material upon initiation is designed to burn, which produces increased pressure in a well interval proximate the fracturing tool. In further implementations, the energetic material can be part of a mixture that further includes proppants, a solid acid, a bactericide (a disinfectant for suppressing bacteria growth in a well), and other materials.

FIG. 1 is a partial sectional view of a fracturing tool 100 in accordance with some implementations. The fracturing tool 100 has a slotted outer housing 102, which has various openings 104. The outer housing 102 can be a metallic housing or a non-metallic housing. The openings 104 are preconfigured or pre-manufactured in the slotted housing 102; in other words, the openings 104 are present in the slotted housing 102 prior to detonation of an explosive element of the fracturing tool 100, as discussed further below.

A first end of the slotted housing 102 is connected to a firing head 106, which can be activated to initiate detonation of an explosive element in the fracturing tool 100. The firing head 106 can be activated by any one of various types of stimuli. For example, the firing head 106 can be electrically activated, such as by transmission of an electrical signal over an electrical cable that is attached to the firing head 106. In other examples, the firing head 106 can be activated using an optical signal provided over an optical cable, by a pressure stimulus, by a mechanical stimulus, and so forth.

The lower end of the fracturing tool 100 is connected to a bottom nose 108, or to some other structure.

The slotted outer housing 102 defines an inner chamber 110. Various components are contained in the inner chamber 110, including an energetic material 112, and an energetic material initiation assembly 114 according to some implementations. The energetic material 112 can be any one of the various example energetic materials listed above. The energetic material 112 is positioned to surround the initiation assembly 114 inside the chamber 110. In some examples, the energetic material 112 can withstand high temperatures (e.g. temperatures greater than 300° F.) or ultra-high temperatures (e.g. temperatures greater than 500° F.).

The energetic material 112 can be formed of a particulate or powder material. Alternatively, the energetic material can be a solid material having a certain shape, such as a cubic shape, spherical shape, or other shape. In further examples, the energetic material 112 can be formed of a liquid, which can be provided in implementations where the outer housing 102 does not have openings 104 (such as implementations according to FIG. 3 discussed further below).

The energetic material 112 can be formed of a water-resistant material. Alternatively, the energetic material 112 can be non-water-resistant, which can be used in the FIG. 3 implementation, for example.

The initiation assembly 114 includes a container structure 116, a loading tube 118 inside the container structure 116, and puncher charges 120 inside the loading tube 118. More specifically, the container structure 116 can be a central tube, in which the loading tube 118 is arranged. Since the central tube 116 is provided in the slotted outer housing 102, the central tube 116 is sealed to protect components inside the central tube 116. The central tube 116 and the loading tube 118 can each be formed of a metallic material or a non-metallic material.

A cross-sectional view of a portion of the fracturing tool, along section 2-2, is depicted in FIG. 2. According to the example of FIGS. 1 and 2, the slotted outer housing 102, central tube 116, and loading tube 118 are generally cylindrical in shape. In other implementations, one or more of the foregoing structures can have other cross-sectional shapes, including non-circular cross-sectional shapes.

The central tube 116 has a larger pressure rating than the loading tube 118, such that the central tube 116 can withstand larger well pressures. The central tube 116 serves to protect components inside the central tube 116 from the increased downhole pressures that may be present in a relatively deep well. Note that the inner chamber 110 of the slotted outer housing 102 is in fluid communication with the well due to presence of the openings 104.

The puncher charges 120 upon detonation are able to create openings in the loading tube 118 and the container structure 116. However, the puncher charges 120 have relatively low explosive power as compared to perforating shaped charges, which are designed to produce perforating jets that have enough power to perforate any surrounding casing or liner and extend perforation tunnels into the formation surrounding the well in which the fracturing tool 100 is provided.

In contrast, the puncher charges 120 are configured without sufficient explosive power to produce perforating jets to perforate the surrounding casing or liner and extend perforation tunnels in the surrounding formation. As a result, using the fracturing tool 100 according to some implementations, fracturing operations can be performed without causing perforation damage to the casing or liner and the surrounding formation.

As depicted in the example of FIG. 1, the puncher charges 120 can be arranged to point in various different directions. For example, the puncher charges 120 can have a spiral pattern along the length of the fracturing tool 100. In other examples, the puncher charges 120 can have different arrangements.

The puncher charges 120 are ballistically connected to a detonating cord 122. The detonating cord 122 is ballistically coupled to the firing head 106, and the detonating cord 122 is initiated by the firing head 106. Upon initiation of the detonating cord 122, the puncher charges 120 are detonated, which causes the puncher charges 120 to produce explosive forces along respective directions to extend openings through the loading tube 118 and central tube 116.

The explosive force of the puncher charges 120 is provided to also initiate the energetic material 112. Initiation of the energetic material 112 produces increased pressure in the well interval surrounding the fracturing tool 100. For example, if the energetic material 112 is implemented with a propellant, initiation of the propellant causes the propellant to burn, which produces gases that increases the pressure in the well interval surrounding the fracturing tool 100. The increased pressure in the well interval surrounding the fracturing tool 100 is sufficient to extend fractures in the surrounding formation.

A relatively reliable initiation assembly 114 is thus provided for initiating the energetic material 112, even in the presence of relatively high downhole pressures in deep wells. Also, since the energetic material 112 is contained within the outer housing 102, inadvertent initiation of the energetic material 112 due to frictional contact can be avoided.

FIG. 3 depicts a fracturing tool 100-1 according to different implementations. In FIG. 3, components that are similar to the corresponding components in FIG. 1 are assigned the same reference numerals. The fracturing tool 100-1 has a scalloped outer housing 302, which is not preconfigured or pre-manufactured with openings as is the case with the slotted outer housing 102 of FIG. 1. Instead, the scalloped outer housing 302 has scalloped regions 304, which are regions of the wall of the scalloped outer housing 302 that are thinner than remaining parts of the wall of the housing 302. The scalloped regions 304 are designed to allow for puncher charges 120 of the fracturing tool 300 to more easily punch openings in the scalloped outer housing 302, upon detonation of the puncher charges 120. The scalloped regions 304 can have various shapes, such as a round shape, rectangular shape, oval shape, or any other shape.

In other implementations, the outer housing 302 can be without the scalloped regions 304 of FIG. 3 or without the openings 104 of FIG. 1. Such an outer housing 302 has a regular wall width.

An energetic material 112 is provided in the inner chamber of the scalloped outer housing 302. Since the scalloped outer housing 302 is sealed against the external well fluids, the energetic material 112 used in the fracturing tool 100-1 of FIG. 3 can have a lower pressure rating than the energetic material 112 used in the fracturing tool of FIG. 1. As a result, greater flexibility in selection of the energetic material 112 can be provided with the fracturing tool 100-1 of FIG. 3, since the energetic material is no longer exposed to well fluids.

The energetic material 112 is provided around an energetic material initiation assembly 114-1, which is similar to the initiation assembly 114 of FIG. 1 except that the central tube 116 of FIG. 1 is omitted. Instead, the initiation assembly 114-1 includes just the loading tube 118 and puncher charges 120 and detonating cord 122 inside the loading tube 118. The central tube 116 in the fracturing tool 100 of FIG. 1 can be omitted in the fracturing tool 100-1 of FIG. 3 since the scalloped outer housing 302 protects the initiation assembly 114-1 from external well fluid pressure.

Effectively, in implementations according to FIG. 3, the scalloped outer housing 302 provides the container structure for protecting components inside the scalloped outer housing 302 from the elevated downhole pressures.

In operation of the fracturing tool 100-1, upon initiation of the detonating cord 122 by the firing head 106, the puncher charges 120 are detonated, which causes explosive forces to break through the loading tube 118 and also to extend openings through the scalloped regions 304 of the scalloped outer housing 302. In addition, detonation of the puncher charges 120 causes initiation of the energetic material 112. The energetic material 112 upon initiation produces elevated pressure, which can be communicated through the openings created through the scalloped regions 304 into the surrounding well interval. The elevated pressure is designed to fracture the surrounding formation.

FIG. 4 illustrates a tool string that is lowered into a well 402. The well 402 can be lined with casing or liner 404, which has been previously perforated with perforations 409. The surrounding formation also has perforation tunnels 411 that resulted from a perforating operation. Alternatively, the tool string can be used in an open hole section of the well 402, where the open hole section is unlined. Although the well 402 is shown as being deviated in the FIG. 4 example, it is noted that in other examples, the well 402 can be a vertical well or a horizontal well. The tool string is lowered on a deployment structure 406, which can be a wireline, tubing (e.g. coiled tubing or other tubing), a pipe, a slickline, and so forth. The tool string has a fracturing tool 408 (which can be the fracturing tool 100 or 100-1 depicted in FIG. 1 or 3, respectively). Activation of the firing head 106 (FIG. 1 or 3) of the fracturing tool 100 or 100-1 can be in response to various stimuli that can be sent from equipment at the earth surface 418 to the firing head 106.

FIG. 5 is a flow diagram of a process of forming a fracturing tool (100 or 100-1 of FIG. 1 or 3) according to some implementations. A container structure (116 or 302 of FIG. 1 or 3) is provided (at 502). A puncher charge (120 in FIG. 1 or 3) is arranged (at 504) in the container structure. In addition, an energetic material (112 in FIG. 1 or 3) to be initiated by the puncher charge is provided (at 506) in the fracturing tool.

In the foregoing description, numerous details are set forth to provide an understanding of the subject disclosed herein. However, implementations may be practiced without some or all of these details. Other implementations may include modifications and variations from the details discussed above. It is intended that the appended claims cover such modifications and variations. 

What is claimed is:
 1. A fracturing apparatus for use in a well, comprising: a container structure; a puncher charge arranged in the container structure, where the puncher charge if detonated is configured to extend an opening through the container structure without creating a perforation tunnel in a formation surrounding the well; and an energetic material to be initiated by detonation of the puncher charge, where the energetic material upon initiation creates an increased pressure in the well to perform fracturing of the formation.
 2. The fracturing apparatus of claim 1, further comprising an outer housing, wherein the container structure is located inside the outer housing.
 3. The fracturing apparatus of claim 2, wherein the energetic material is between the outer housing and the container structure.
 4. The fracturing apparatus of claim 2, further comprising a loading tube carrying the puncher charge, the loading tube being inside the container structure, wherein the container structure is to provide protection of an assembly including the loading tube and puncher charge from well pressure.
 5. The fracturing apparatus of claim 2, wherein the outer housing has an opening that exists prior to detonation of the puncher charge, wherein the opening provides for fluid communication between an inner chamber of the outer housing and the well.
 6. The fracturing apparatus of claim 1, wherein the container structure is an outer housing of the fracturing apparatus.
 7. The fracturing apparatus of claim 6, wherein the container structure has a scalloped region through which an explosive force of the puncher charge is to extend to create an opening in the container structure.
 8. The fracturing apparatus of claim 6, further comprising a loading tube carrying the puncher charge, where the energetic material is between the loading tube and the container structure.
 9. The fracturing apparatus of claim 1, wherein the energetic material is selected from the group consisting of a propellant, a high explosive, a gun powder, a combustible metallic powder, thermite, or a combination thereof.
 10. The fracturing apparatus of claim 1, wherein the well is lined with a casing or liner, and wherein the puncher charge if detonated is configured to extend the opening through the container structure without perforating the casing or liner.
 11. The fracturing apparatus of claim 1, wherein the energetic material is part of a mixture that further includes at least one selected from the group consisting of proppants, a solid acid, a bactericide, and a combination thereof.
 12. A method of forming a fracturing apparatus for use in fracturing a formation around a well, comprising: providing a container structure; arranging puncher charges inside the container structure, wherein the puncher charges if detonated extend openings through the container structure without creating perforation tunnels in the formation; and providing an energetic material in the fracturing apparatus to be initiated by detonation of the puncher charges.
 13. The method of claim 12, further comprising ballistically connecting a detonating cord to the puncher charges.
 14. The method of claim 12, further comprising arranging the puncher charges within a loading tube that is inside the container structure.
 15. The method of claim 12, further comprising providing the container structure and the energetic material inside an outer housing that has pre-configured openings to allow fluid communication between the well and an inner chamber of the outer housing.
 16. The method of claim 12, wherein the container structure is a scalloped outer housing having thinned wall regions through which the puncher charges are to extend openings upon detonation of the puncher charges.
 17. A system comprising: a tool string for deployment into a well, the tool string having a fracturing tool, the fracturing tool comprising: a container structure; a puncher charge arranged in the container structure, where the puncher charge if detonated is configured to extend an opening through the container structure without creating a perforation tunnel in a formation surrounding the well; and an energetic material to be initiated by detonation of the puncher charge, where the energetic material upon initiation creates an increased pressure in the well to perform fracturing of the formation.
 18. The system of claim 17, wherein the energetic material is selected from the group consisting of a propellant, a high explosive, a gun powder, a combustible metallic powder, thermite, or a combination thereof.
 19. The system of claim 17, wherein the fracturing tool further comprises an outer housing in which the container structure is located, the outer housing having an opening.
 20. The system of claim 17, wherein the container structure is a scalloped outer housing. 